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| Home > Publications database > Correlation effects in two-dimensional M X 2 and M A 2 Z 4 ( M = Nb , Ta ; X = S , Se , Te ; A = Si , Ge ; Z = N , P ) cold metals: Implications for device applications |
| Home > Publications database > Correlation effects in two-dimensional M X 2 and M A 2 Z 4 ( M = Nb , Ta ; X = S , Se , Te ; A = Si , Ge ; Z = N , P ) cold metals: Implications for device applications |
| Journal Article | FZJ-2025-01134 |
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2025
APS
College Park, MD
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Please use a persistent id in citations: doi:10.1103/PhysRevMaterials.9.014006 doi:10.34734/FZJ-2025-01134
Abstract: Cold metals, characterized by their distinctive band structures, hold promise for innovative electronic devices such as tunnel diodes with negative differential resistance (NDR) effect and field-effect transistors (FETs) with sub-60 mV/dec subthreshold swing (SS). In this study, we employ the 𝐺𝑊 approximation and HSE06 hybrid functional to investigate the correlation effects on the electronic band structure of two-dimensional cold metallic materials, specifically focusing on 𝑀𝑋2 and 𝑀𝐴2𝑍4 (𝑀=Nb, Ta; 𝑋=S, Se, Te; 𝐴=Si, Ge; 𝑍=N, P) compounds in 1H structure. These materials exhibit a unique band structure with an isolated metallic band around the Fermi energy, denoted as 𝑊m, as well as two energy gaps: the internal gap 𝐸Ig below the Fermi level and the external gap 𝐸Eg above the Fermi level. These three electronic structure parameters play a decisive role in determining the current-voltage (𝐼−𝑉) characteristics of tunnel diodes, the nature of the NDR effect, and the transfer characteristics and SS value of FETs. Our calculations reveal that both 𝐺𝑊 and HSE06 methods yield consistent electronic structure properties for all studied compounds. We observed a consistent increase in both internal and external band gaps, as well as metallic bandwidths, across all pn-type cold metal systems. Notably, the internal band gap 𝐸Ig exhibits the most substantial enhancement, highlighting the sensitivity of these materials to correlation effects. In contrast, the changes in the metallic bandwidth 𝑊m and external band gap 𝐸Eg are relatively modest. These findings offer valuable insights for designing and optimizing cold metal-based devices. Materials like NbSi2N4, NbGe2N4, and TaSi2N4 show particular promise for high-performance NDR tunnel diodes and sub-60 mV/dec SS FETs.
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